We have already characterized and partially purified a collagenase, neutral metal protease produced by several metastatic tumors, which specifically degrades basement membrane (type IV) collagen. We also have correlated the metastatic potential in vivo of different tumor cell lines with the production of this enzyme. We are trying to obtain an antiserum on this enzyme to better understand the mechanism of activity on the substrate and the effective role of this collagenase in the metastatic process. We have also identified that specific glycoproteins mediate interactions of tumor cells to basement membrane. We have identified a new receptor on human breast carcinoma cells which mediates this interaction.